Error: Set not JSON Serializable while converting TSV File into JSON Format using Python

Question

I'm looking to convert a TSV File I have into JSON Format for mapping (google fusion maps doesn't support mapping multiple objects in the same location so I'm converting it to JSON format to try on Mapbox). Here's my TSV file if you're curious:

https://github.com/yongcho822/Movies-in-the-park/blob/master/MovieParksGeocodeTest.tsv

And here is my corresponding python code thus far:

import json
import csv

def create_map(datafile):
    geo_map = {"type":"FeatureCollection"}
    item_list = []
    with open(datafile, 'r') as tsvfile:
        reader = csv.DictReader(tsvfile, delimiter = '\t')

        for i, line in enumerate(reader):
            data = {}
            data['type'] = 'Feature'
            data['id'] = i
            data['properties']={'title': line['Movie Title'],
                               'description': line['Amenities'],
                               'date': line['Date']}
            data['name'] = {line['Location']}
            data['geometry'] = {'type':'Point',
                               'coordinates':(line['Lat'], line['Lng'])}
            item_list.append(data)
        #print item_list
        for point in item_list:
            geo_map.setdefault('features', []).append(point)
        print 'CHECKPOINT'
        with open("thedamngeojson.geojson", 'w') as f:
            f.write(json.dumps(geo_map))

create_map('MovieParksGeocodeTest.tsv')

It's throwing me an error at the end (after it prints CHECKPOINT), saying

TypeError: set(['Edgebrook Park, Chicago ']) is not JSON serializable

I figure the last two lines is where the error is.. but what's wrong and how do I fix it??

Answer 1

JSON is designed to be a very simple, very portable format; the only kinds of values it understands are strings, numbers, booleans, null (like Python None ), object s (like a Python dict ) and array s (like a Python list ).

But at least one of the values in your dictionary is a set :

data['name'] = {line['Location']}

Since JSON doesn't have a set type, you get an error telling you that set … is not JSON serializable .

If you don't actually need this to be a set instead of a list (which you probably don't—if it really only ever have one element, who cares which collection type it is?), the easy answer is to change it to be a list :

data['name'] = [line['Location']]

(In fact, even when you do need this to be a set during processing, you usually don't need it to be a set during storage/interchange. If the consumer of your file needs to use it as a set, it can always convert it back later.)